Films of organic materials, commonly referred to as photoresists, are recording media on which information can be recorded in the form of a relief pattern. Such media, when exposed to a light pattern, change their solubility characteristics in those areas struck by the light. Films of photoresists are developed by contacting them after exposure in a controlled manner with a developer solution which is a solvent that dissolves the more soluble portions of the films, leaving the less soluble portions in a relief pattern which corresponds to the information contained in the light pattern. Negative photoresists are initially soluble in the developer solution and exposed portions become insolubilized. Positive photoresists are initially insoluble and become more soluble in the developer solution in the exposed portions.
Suitably modulated electron beams have also been utilized for recording relief patterns. Electron beams, by virtue of their shorter effective wavelength and greater depth of focus, can record information at higher resolution or density than can light beams. This ability is highly useful in the fabrication of integrated circuitry having very small circuit elements employing processes using electron beam sensitive materials and conventional photoresist processing techniques. Positive electron beam sensitive materials are also useful in serial information recording whereby individual signal elements are formed as minute, well-defined depressions in the surface of the electron beam sensitive material.
Formulations such as naphthoquinone diazide sulfonic acid esters admixed with an alkali soluble resin have long been utilized as positive photoresists in the lithographic art. These formulations form resist films which, after exposure to light or electron beams, are developed by contacting the films with appropriate aqueous alkaline solutions. Formulations of this type employing certain preferred naphthoquinone diazides admixed with an alkali soluble resin have also been found to be particularly useful as electron beam resists. One particular compound, 2,4-bis(6-diazo-5,6-dihydro-5-oxo-1-naphthalenesulfonyloxy)benzophenone, admixed with an alkali soluble resin in certain proportions, e.g. to contain from about 1 to about 50% by weight of the above compound, produces a formulation found to be particularly sensitive to electron beams, as is disclosed in copending application of Ross and Barton, Ser. No. 332,025, filed Feb. 12, 1973 now U.S. Pat. No. 3,852,771, issued Dec. 3, 1974, herein incorporated by reference.
Currently known electron beam sensitive formulations vary considerably in their sensitivity and resolution capabilities which in turn limits the density of recorded information obtainable. Accordingly, means for improving the sensitivity and resolution of electron beam recording media would be highly desirable.